this happens to my parents its a loose connection between cord and the screen itself try getting a new screen. if not then don’t know how else to solve it other than getting a new chip
sorry but I have limited info for you if you have a multimeter if you see this fuse on it when you open it and test it if something goes though then the backlight fuse is fine then test all diodes (if you are a kid then they only let power go though one way so test with positive and negative on both sides) red is positive black is negative) the picture is this website to get one of them if you need one
yes that is the water you are right on that, however, getting out the water may be hard take it apart and try to find the water then take a dry cloth and remove it then put back together.
so sounds like you got hacked/ have a virus so what that is when you surf the web and click on some ad sometimes it downloads something that gives the people who made the program control over your computer you can try to get in and run a virus scan(ONLY TRUSTED ONES NOT SOME RANDOM YOU SEE ON THE INTERNET)and get rid of it but can't do much if it types random things if that does not work you can factory reset(you will lose all pics apps etc) or contact your provider.
if you smell burning it was caused by electricity and is melting/ burning something change USB adaptor see if that works if not change the charging board in the phone.
uhhh it will work without anything but battery and board however i would not suggest it. you may have shorted something that runs the screen if you got a new screen replace it and see if that works